Pay protection reg

Hi This is Sateesh working as senior clerk in rlys, presently iam drawing 12430 basic(9630+2800 gp).in 7th PC as per formula my basic fixed at 31000 as on 1.1.2016, Recently I got selected as tax asst in income tax with GP 2400, how the pay protection will be done as per 7th PC and what is my basic after shifting down the gp from 2800 to 2400 in 7th pc